The maximum deflection of a blade row of a turbomachine and thus its aerodynamic strength are delimited, on the one hand, by a flow separation on the blade profile. On the other hand, the maximum deflection is delimited by a separation of a boundary layer flow at the hub- and the housing-side side walls. To increase the deflectability of the blade rows, double-row blade arrangements are known. A known turbomachine having such an arrangement is shown in FIG. 1. It has a hub 2 which is rotatably mounted in a housing 4 around a rotor axis 6 extending in longitudinal direction x. Hub 2 and housing 4 delimit an annular main flow path 8 through which there is a flow from left to right according to the horizontal arrow and in which a rotor-side blade row group 10, a stator-side blade row group 12, and an adjustable blade row group 14 are situated, for example. Blade row groups 10, 12, 14 each have two blade rows which include a plurality of blades 16, 18 and which are situated one after another in the flow direction. For the sake of clarity, the rotor-side blade row group is preferably provided with reference numeral 10 in the following. Rotor-side blade row group 10 and stator-side blade row group 12 are each fixedly connected to hub 2 and to housing 4, a gap 20 being formed between the blade tips of blades 16, 18 and housing 4 and hub 2. Blades 16, 18 of adjustable blade row group 14 are each mounted at their ends on a rotary disk 22, 24 and are pivotable around a transverse axis 26 according to the rotary arrow. Front blades 16 each have a rear edge 28 facing one of rear blades 18. Rear blades 18 each have a front edge 30 facing one of front blades 16. Edges 28, 30 have a linear shape and extend radially almost transversely to the transverse flow direction, so that a constant axial edge distance is formed between edges 28, 30 and thus between blades 16, 18. Furthermore, a constant edge distance in the peripheral direction is formed between edges 28, 30. Moreover, a blade 32 of a single rotor blade row is shown in FIG. 1.
However, it has been found that in the side wall area, i.e., in the area of hub 2 and/or of housing 4, a blade contour is necessary, due to the influence of the boundary layer, which deviates from a main flow path center 34 and with the aid of which the flow conditions in the side wall area, which are changed with regard to main flow path center 34, may be considered. In EP 2 261 463 A2, it is therefore proposed for blade row groups to set a meridional distance between the rear edges of the front blades and the front edges of the rear blades in such a way that this distance increases starting from a main flow path center in the direction of a hub- or housing-side side wall.
In DE 697 30 663 T2, a turbomachine having a tandem cascade is shown in which starting from a main flow path center a periphery-side edge distance between a particular front edge of an upstream blade row and a particular rear edge of a downstream blade row increases in the direction of a tip-side main flow limitation and decreases in the direction of a hub-side main flow limitation. The periphery-side edge distance according to DE 697 30 663 T2 thus has different algebraic signs starting from main flow path center.